Implement deploy trigger in release-tools
After #576 (closed) we now need to take the deploy trigger which is located in omnibus-gitlab and implement it into release-tools.
The original trigger is called after the Ubuntu 16 upload: https://gitlab.com/gitlab-org/omnibus-gitlab/-/blob/3335da0faabedf6fbabb30089f312b283fec4a20/gitlab-ci-config/dev-gitlab-org.yml#L406
And this trigger is initiated by a rake task built into omnibus-gitlab: https://gitlab.com/gitlab-org/omnibus-gitlab/-/blob/3335da0faabedf6fbabb30089f312b283fec4a20/lib/gitlab/tasks/gitlab_com.rake#L6
We should be able to move all of this over into release-tools. The trigger should happen after we wait on the auto-deploy tag to omnibus.
In the beginning, we will run this trigger in parallel with one in omnibus, while we work on the deployer refactoring &362 the target branch for the trigger must be the next-gen
branch that will ensure a dry-run of the deployer.